OPINION: Why pizza oven extract design needn’t be a headache

More and more foodservice companies are opting for wood-fired pizza ovens to bring theatre and sales to their operation. For those that are new to this area, there are some basic principles that should be considered when choosing this type of installation, writes Sam Ford of Chimflue.

There has been huge growth in the wood-fired pizza oven market over the last five years and this has led to us installing systems in a wide range of sites from Edinburgh to St Ives, Manchester to Dover, holiday parks to zoos, and historic buildings to stunning new sky scrapers.

One common factor to any new or existing restaurant considering a wood-fired pizza oven installation is that the extract system should be considered as early as possible. This is to ensure that a safe, suitable and reliable design can be achieved within the available space and taking into account any site-specific constraints.

Building types

It is important to consider the location of the restaurant in relation to any adjoining buildings or office space / accommodation directly above the restaurant itself. The flue system for your wood-fired oven will need to terminate above any close by or adjoining buildings and in some cases this can lead to huge flue runs which can have a considerable cost.

Local authority planning & EHO permissions

One essential part of the process is to establish at an early stage what the local requirements are for the installation of your proposed wood-fired oven and flue system. If within a smoke control zone, you will need to install a DEFRA-approved oven — this is essentially an oven which has been tested and approved by DEFRA and a full list of these can be found on their website.

In addition to DEFRA approval you may find that your local planning department and / or environmental health officer may want you to install filtration to the extract system. This will help to reduce the particulate discharged to atmosphere and the potential of nuisance odours. The other main factor that planning departments will also want to check is the visual appearance of the system. When rising externally we are often asked to powder-coat flue systems in various colours or in some cases hand paint the case of the flue itself so it blends in with the existing structure.

Flue sizing and routing

Flue sizes for this type of installation are usually 200mm or 250mm internal diameter so once insulation is included you will need to take into account a system of 264mm or 314mm external diameter running throughout the restaurant to the required riser location.

One of the most critical elements of system design is making sure that good, easily accessible points for inspection and cleaning of the system are available throughout the route of the flue. In most restaurants we work in, the flue system is left on show as a feature but where it is to be enclosed you will need to make sure that corresponding access hatches are installed within any false ceilings to allow access to the flue.

Flue types & finishes

You must ensure you have a dedicated twin wall insulated flue system installed when specifying a wood-fired pizza oven. This flue needs to be CE approved, have a designation for high continuous flue gas temperatures (T450) and a four-hour fire rating where passing through internal and external fire-rated partitions.

At Chimflue we use a system with a 32mm insulation cavity and this allows a minimum clearance from combustible materials of 50mm — often 75mm from other manufacturers. The systems we provide are available in three standard finishes — stainless steel, matt black and copper. It is also possible to powder-coat these systems to any RAL or BS colour meaning you can get creative where the system runs through your restaurant or assist in blending to the existing finishes when running externally.

Extract system requirements need to be planned into a project as early as possible.

Exodraft fan systems

In most restaurants you will find that the flue system will need to run horizontally at some point when making its way towards the riser. In addition to this, it is not uncommon to find general extract systems and kitchen canopies within the same space of the flue.

Due to these factors 99% of the systems we install for pizza ovens will include a fan system. This is used to guarantee flue draft regardless of the resistance created by horizontal flue runs and negative pressures from other extracts. Exodraft is the only way to go when it comes to fans for solid fuel ovens and they offer a wide range of units that will cover all eventualities. These fans are installed at the exit point of the flue and so again consideration needs to be given to the ability to access and maintain these systems.

Filtration systems

The final crucial factor to consider when installing a wood-fired pizza oven is whether to fit a filtration unit to reduce the output of particulate and odours from the system. The ovens usually run between 400°C and 500°C and the subsequent flue gas temperature can be in the region of 250°C to 300°C. This sort of temperature is far outside of the range of ESP and carbon filtration, and so the only way to go is a water-based filtration unit.

Chimflue is the UK importer for SMOKI, which is a water-based filtration system specifically designed and manufactured in Italy for use with pizza ovens. A SMOKI unit requires a permanent mains water, foul drainage and electrical connection, and again these services need to be taken into account with your plans.

The system passes all smoke from the oven through three layers of fine water mist within the unit, which removes a large proportion of particulate from the smoke. As a by-product, this process also reduces the odour produced from the flue’s termination and is often specified as a requirement by local planning officers and EHOs.

Maintenance considerations

One of the most important issues to keep in mind after the oven starts operating is regular planned maintenance of the flue system, fan and filtration unit where installed. This is key to ensure the longevity of the system and to make sure it remains safe and suitable for use.

For solid fuel cooking in commercial environments, the maintenance regimes will vary dependant on oven usage, design of system and the restaurant’s own risk assessments but we always recommend a minimum of twice a year for a full clean and inspection. A lot of our customers utilise a quarterly regime.

Sam Ford is managing director of Chimflue, a specialist in the design, supply and installation of flue, chimney and exhaust systems for commercial pizza ovens and other types of appliances. www.chimflue.co.uk